Crowding and eccentricity determine reading rate
Crowding and eccentricity determine reading rate
复制标题
DOI：
10.1167/7.2.20
复制
发表时间：
2007-01-01
影响因子：
1.8
通讯作者：
Majaj, Najib J.
中科院分区：
文献类型：
--
作者：
Pelli, Denis G.;Tillman, Katharine A.;Majaj, Najib J.
布玛的拥挤定律预言了一个不拥挤的中心窗口，我们可以通过它阅读，而一个拥挤的外围，我们不能通过它。阅读者每秒钟会进行几次注视，而不是连续地扫过文本，这一古老的发现表明，阅读受到一次注视中可以获得的字母数量的限制，而不需要移动眼睛。这种“视觉广度”已经用各种方法测量过了，但仍然无法解释。在这里，我们表明：（1）视觉跨度仅仅是不拥挤的字符的数量;（2）在每个垂直偏心率下，阅读率与不拥挤的跨度成正比。我们测量快速串行视觉呈现（RSVP）的阅读率的文本，在原始和混乱的词序，作为一个功能的大小和间距在中央和外围位置。随着文本大小的增加，阅读速率从零突然上升到最大速率。这个经典的阅读速率曲线由悬崖和平台组成，其特征在于两个参数，临界打印尺寸和最大阅读速率。将文献中的两个概念结合起来就可以解释整个曲线。这两个概念分别是布玛拥挤定律和理雅各的阅读速度与视觉广度成正比的猜想。我们表明，莱格的视觉跨度是不拥挤的布玛定律预测的跨度。这个结果结合了Bouma和Legge来解释阅读率对字母大小和间距的依赖。矫正良好的流畅观察者在光线充足的情况下阅读普通文本时，受到字母间距（拥挤）的限制，而不是大小（敏锐度）。更一般地说，这个解释似乎是正确的，与大小、对比度和亮度无关，只要文本对比度至少是孤立字母阈值对比度的四倍。对于任何给定的间距，都有一个中心的不拥挤的跨度，我们通过它阅读。这个不拥挤的跨度模型解释了阅读率曲线的形状。我们以几种方式测试该模型。我们使用“无声替代”技术来测量阅读过程中的非拥挤广度。这些替换破坏了字母识别，但当字母拥挤时无法检测到。临界间距是避免拥挤的字母之间的最小距离。我们发现，字母识别的临界间距预测了临界间距和阅读的广度。因此，拥挤预测表征阅读速率曲线的悬崖和平台的参数。先前的研究发现，在普通文本的测量外围阅读率方面，观察者和实验室之间存在令人担忧的差异，这可能反映了印刷品暴露的差异，但我们发现，当词序混乱时，阅读率更加一致。在测试的所有条件下--所有尺寸和间距，中心和外围，有序和混乱--阅读都受到拥挤的限制。对于每个观察者，在每个垂直偏心率下，阅读速率与不拥挤跨距成正比。
Bouma's law of crowding predicts an uncrowded central window through which we can read and a crowded periphery through which we cannot. The old discovery that readers make several fixations per second, rather than a continuous sweep across the text, suggests that reading is limited by the number of letters that can be acquired in one fixation, without moving one's eyes. That "visual span" has been measured in various ways, but remains unexplained. Here we show ( 1) that the visual span is simply the number of characters that are not crowded and ( 2) that, at each vertical eccentricity, reading rate is proportional to the uncrowded span. We measure rapid serial visual presentation ( RSVP) reading rate for text, in both original and scrambled word order, as a function of size and spacing at central and peripheral locations. As text size increases, reading rate rises abruptly from zero to maximum rate. This classic reading rate curve consists of a cliff and a plateau, characterized by two parameters, critical print size and maximum reading rate. Joining two ideas from the literature explains the whole curve. These ideas are Bouma's law of crowding and Legge's conjecture that reading rate is proportional to visual span. We show that Legge's visual span is the uncrowded span predicted by Bouma's law. This result joins Bouma and Legge to explain reading rate's dependence on letter size and spacing. Well-corrected fluent observers reading ordinary text with adequate light are limited by letter spacing (crowding), not size (acuity). More generally, it seems that this account holds true, independent of size, contrast, and luminance, provided only that text contrast is at least four times the threshold contrast for an isolated letter. For any given spacing, there is a central uncrowded span through which we read. This uncrowded span model explains the shape of the reading rate curve. We test the model in several ways. We use a "silent substitution" technique to measure the uncrowded span during reading. These substitutions spoil letter identification but are undetectable when the letters are crowded. Critical spacing is the smallest distance between letters that avoids crowding. We find that the critical spacing for letter identification predicts both the critical spacing and the span for reading. Thus, crowding predicts the parameters that characterize both the cliff and the plateau of the reading rate curve. Previous studies have found worrisome differences across observers and laboratories in the measured peripheral reading rates for ordinary text, which may reflect differences in print exposure, but we find that reading rate is much more consistent when word order is scrambled. In all conditions tested-all sizes and spacings, central and peripheral, ordered and scrambled-reading is limited by crowding. For each observer, at each vertical eccentricity, reading rate is proportional to the uncrowded span.